STEADY DEFLAGRATION OF HMX WITH SIMPLE KINETICS - A GAS-PHASE CHAIN-REACTION MODEL

A new approach is presented for modeling steady combustion of energeti c solids, in particular HMX. A simplified, global, gas phase chain rea ction kinetic mechanism is employed. Specifically, a zero-order, high activation energy thermal decomposition initiation reaction in the con densed phase followed by a second-order, low activation energy chain r eaction in the gas phase is assumed. A closed-form solution is obtaine d, which is based on the activation energy asymptotics analysis of Len gelle in the condensed phase and the assumption of zero activation ene rgy in the gas phase. Comparisons between the model and a variety of e xperimental observations over a wide range of pressures and initial te mperatures are presented and demonstrate the validity of the approach. The model provides excellent agreement with burning rate data (includ ing sensitivity to pressure and initial temperature) and temperature p rofile data (in particular the gas phase). This suggests that in the r ealm of simplified, approximate kinetics modeling of energetic solids, the low gas phase activation energy limit is a more appropriate model than the classical high activation energy limit or heuristic flame sh eer models. The model also indicates that the condensed phase reaction zone plays an important role in determining the deflagration rate of HMX, underscoring the need for better understanding of the chemistry i n this zone. (C) 1998 by The Combustion Institute.